1. Field of the Invention
The present invention relates to a technology of a mirror drive apparatus including a movable unit with a mirror provided therein and used to switch an optical path.
2. Description of the Related Art
A single-lens reflex camera (imaging apparatus) typically includes a mirror box (mirror drive apparatus) configured as what is called a quick-return mirror insertable and retractable to and from the optical path of an imaging lens. The mirror box includes a primary mirror holder with a primary mirror provided therein and a secondary mirror holder with a secondary mirror provided therein, the primary and secondary mirror holders capable of changing their positions between an inserted position in which the primary and secondary mirrors are inserted to the optical path and a retracted position in which the primary and secondary mirrors are retracted from the optical path. Each of the mirror holders is positioned in the inserted position when one side of the mirror holder abuts a stopper (positioning member).
When the secondary mirror in the retracted position is driven and shifted to the inserted position, the secondary mirror holder hits the stopper and is brought to an abrupt halt, which disadvantageously causes the secondary mirror holder to vibrate. Not until the vibration subsides, for example, can a phase-difference AF sensor that receives subject light reflected off the secondary mirror detect the focus (measure the distance) in a precise manner.
JP-A-9-274250, for example, discloses a technology for reducing the vibration of the secondary mirror holder described above. The disclosed technology prevents the secondary mirror holder from vibrating by sandwiching the secondary mirror holder in the inserted position with a pair of pins that serve as the stopper.